overriding variable types

Blake · #1 23-Jun-2006, 15:57

I've defined several classes for doing interpolation. They are:

Interpolator: The interpolator base class.
Scalar Interpolator: Interpolates scalars. Inherits from Interpolator.
QuaternionInterpolator: Interpolates quaternions. Inherits from Interpolator.
Keyframe: The keyframe base class.
ScalarKeyframe: A Keyframe used in scalar interpolation. Inherits from Keyframe.
QuaternionKeyframe: A Keyframe used in quaternion interpolation. Inherits from keyframe.

Each interpolator has an stl map containg Keyframe pointers and time values (floats). The map is contained in the base class so that I can define all the iterator functions, etc, there, rather than redefining them in both leaf classes. The one annoying thing is that I always need to cast a Keyframe* as either a ScalarKeyframe* or QuaternionKeyframe* when I dereference an iterator. Is there a way to override the typedefs in the leaf classes that will prevent that problem? I couild fix it be overriding the function definitions, but I would rather not do that.

Here's the interpolator header (QuaternionInterpolator not shown because it is still a work in progress). The list of virtual functions that return iterators in the Interpolator class are the ones causing problems.

CPP / C++ / C Code:

#include "keyframe.h"
#include <map>

typedef enum {REP_ABS, REP_REL, FLAT} OBType;

//----------------------------------------------------------
// Interpolator Base Class

class Interpolator
{
	public:
		typedef std::map<float, Keyframe *, std::less<float> > KeySet;
		typedef KeySet::iterator iterator;
		typedef KeySet::reverse_iterator reverse_iterator;
		typedef KeySet::const_iterator const_iterator;
		typedef KeySet::const_reverse_iterator const_reverse_iterator;
		Interpolator();
		Interpolator(const Interpolator&);
		virtual float fixRange(const float&);
		virtual void setLeftOB(const OBType& OB) {leftOB = OB;}
		virtual void setRightOB(const OBType& OB) {rightOB = OB;}
		virtual bool empty() {return keyframes.empty();}
		virtual unsigned int size() {return keyframes.size();}
		virtual iterator find(const float& t) {return keyframes.find(t);}
		virtual iterator upper_bound(const float& t) {return keyframes.upper_bound(t);}
		virtual iterator lower_bound(const float& t) {return keyframes.lower_bound(t);}
		virtual iterator begin() {return keyframes.begin();}
		virtual const_iterator begin() const {return keyframes.begin();}
		virtual iterator end() {return keyframes.end();}
		virtual const_iterator end() const {return keyframes.end();}
		virtual reverse_iterator rbegin() {return keyframes.rbegin();}
		virtual const_reverse_iterator rbegin() const {return keyframes.rbegin();}
		virtual reverse_iterator rend() {return keyframes.rend();}
		virtual const_reverse_iterator rend() const {return keyframes.rend();}
	protected:
		KeySet keyframes;
		float startTime;
		float endTime;
		float length;
		OBType leftOB;
		OBType rightOB;
};

//----------------------------------------------------------
// Scalar Interpolator

class ScalarInterpolator : public Interpolator
{
	public:
		typedef std::map<float, Keyframe *, std::less<float> > KeySet;
		typedef KeySet::iterator iterator;
		typedef KeySet::reverse_iterator reverse_iterator;
		typedef KeySet::const_iterator const_iterator;
		typedef KeySet::const_reverse_iterator const_reverse_iterator;
		ScalarInterpolator();
		ScalarInterpolator(const ScalarInterpolator&);
		~ScalarInterpolator();
		void operator=(const ScalarInterpolator&);
		void addKeyframe(ScalarKeyframe *, const float&);
		void addKeyframe(const ScalarKeyframe&, const float&);
		float operator()(const float& t) {return position(t);}
		float position(const float&);
		float velocityIn(const float&);
		float velocityOut(const float&);
		float accelerationIn(const float&);
		float accelerationOut(const float&);
		float jerkIn(const float&);
		float jerkOut(const float&);
	private:
		void updatePrevNext(const float&);
		iterator prevKey;
		iterator nextKey;
		float displacement;
};

And the keyframe header (QuaternionKeyframe not shown for the same reason)

CPP / C++ / C Code:

#include "quaternion.h"

struct Keyframe
{
	Keyframe(const float& f) : keyValue(f) {}
	float keyValue;
};

//----------------------------------------------------------
// Scalar Keyframe

struct ScalarKeyframe : public Keyframe
{
	ScalarKeyframe()
		: Keyframe(0), tangentIn(0), tangentOut(0) {}
	ScalarKeyframe(const float& p, const float& v)
		: Keyframe(p), tangentIn(v), tangentOut(v) {}
	ScalarKeyframe(const float& p, const float& v1, const float& v2)
		: Keyframe(p), tangentIn(v1), tangentOut(v2) {}
	float tangentIn;
	float tangentOut;
};

I'm using MS Visual C++ (the free version) on Windows XP Professional.

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